Self-synchronizing system



Nov. 24, 1942. D N ETAL 2,303,115

SELF-SYNCHRONIZING SYSTEM Filed June 21, 1939 3 Sheets-Sheet 1 FIG.

, \NVENTORS.

z Q Frank L. Eidmann George C. Eng! Adolph Amznd, Jr. BY 7 ATTORNEY.

Nov. 24, 1942. E|DMANN ETAL, 2,303,115

' SELF-SYNCHRONIZING SYSTEM Filed June 21, 1939 3 Sheets-Sheet 2 FIG 4' INVENTORS.

FranK L. Eidmann Emerge. C. Engl Add h Amend, Jr. BY

FI G.3

A TTORNEY.

NOV. 24, 1942. L, D NN ETAL 2,303,115"

SELF-SYNCHRONI Z ING SYSTEM Filed June 21, 1959 3 Sheets-Sheet 3 FIG. 6

INVENTURS. Frank L. Eidmu m Georg: C. E ngd Adolph Ammnd. Jr. BY

ATTORNEY.

Patented Nov. 24, 1942 UNITED STATES. PATENT OFFICE 2,303,115 SELF-SYNCHRONIZING SYSTEM Frank L. Eidmann, Princeton, George C. Engel, Ridgewood, and Adolph Amend, Jr., Hoboken, N. J., assignors to General Time Instruments Corporation, New York, N. Y., a corporation of Delaware Application June 21, 1939, Serial No. 280,244

6 Claims.

distance from the generator-and the stators of which are in circuit with the stator" of the generator.

Actually, the generator is a transformer, the rotor being the primary and the stator the secondary. The stator comprises three or more windings in which are induced alternating cursixty cycle voltage is impressed on the primary and the primary rotated five times per hour, on

the three wires leading from the secondary will be found threesixty cycle per second voltages,

.ample are connected to three self-synchronizing reproducer windings on the stator of each reproducer, the reproducer windings being positioned and connected to each other and to the three wire lines in the same manner as the three secondary windings of the rotary-transformer.- A resultant field is induced by the stator windings which rotates five times per hour, or which. one might say, rotates in synchronism with the primary of the rotary transformer.

It has been found, however, that the reproducer rotor, whether it be wound or unwound,

Putting will not rotate in exact synchronism with the five cycle per hour rotating field but that there is a periodic error of as much as plus or minus six degrees between the position of the reproducer rotor and synchronous position or the position of the transformer rotor. This error was found with a twelve-pole stator and was somewhat re-' duced by using a thirty-pole stator in both transformer and reproducer. The error is no doubt caused in part by the lack of an evenly distributed winding and may be reduced by increasing the number of poles or windings, although this is not practical from the standpoint of cost.

'In many applications of such a self-synchronizing system, this periodic error detracts greatly from its value. If, for example, a secondary clock employing this system were to indicate the time first a minute slow and then a minute fast,

it would be valueless.

We have found that this error may be greatly reduced by an improved rotor construction and the greatly reduced error maybe still further reduced until of negligible extent by appropriate gear reduction between the reproducer rotor and the rotatable indicating or control means. Gear reduction to decrease the periodic error adds additional complications to a self-synchronous system, for if the maximum limits between which the rotors of the transformer and reproducer rotate exceeds degrees in the case of an unwound rotor, or 360 degrees in the case of a wound rotor for the reproducer, accumulator means must be provided to insure that the reproducer rotor rotates through the same number of half or complete rotations as the generator rotor, even though no current is induced in the stator circuit due to interruption in the current supply to the generator rotor.

Consequently in applications of the system where the rotating member coupled to the transformer rotor does not change its position beyond maximum limits of 180 degrees or 360 degrees, the periodicerror may best be reduced by the use of our improved rotor construction alone without gear reduction.

However, in certain applications, where the rotating member coupled to the transformer rotor rotates beyond 360 degrees or rotates continuously in one direction, accumulator means must be used even though the two are coupled in a one to one speed ratio. In these instances, gear reduction may well be used to reduce the periodic error for the accumulator means must be employed whether gear reduction is used or not. A secondary clock system is an example of these latter applications in which an accumulator is necessary and in this application it is desirable to employ both gear reduction and the above mentioned improved rotor construction to obtain the necessary accuracy. Consequently, our improved self-synchronizing system is described herein as applied to a clock system.

Although it has been previously proposed to move the hands of a secondary clock in a clock system by means of a self-synchronizing reproducer, it is well known that none of these clock systems possessed the necessary accuracy. Furthermore, the accumulator means, or means for resetting the hands after a current interruption .required a very complex system often requiring two controls, a coarse and a fine control, and a separate self-synchronizing system for each. The cost of such a clock system prevented it from coming into general use for the ordinary inexpensive clock systems.

An object of our invention is to provide an improved alternating current self-synchronizing system having a high degree of accuracy.

A further object is to provide an improved selfsynchronizing system for the transmission of rotation greater than 360 degrees.

A further object is to provide a simple and inexpensive electric system whereby rotation of one master unit may be reproduced in a large number of reproducer units positioned at consid erable distances from the master unit.

A further object is to provide an improved three wire self-synchronizing system.

A further object is to provide a self-synchronized system which is adapted for incorporation in a secondary clock system.

A further object is to provide an inexpensive secondary clock system of simple construction and of positive eflicient operation.

A further object is to provide an improved rotor construction for a self-synchronizing reproducer.

A further object 'is to provide an improved secondary clock system wherein the secondaries will correct themselves after a current interruption.

Figure 1 is a diagrammatic view of the transmitting unit, the elements being shown in perspective;

Figure 2 is a wiring diagram of the complete system;

Figure 3 is an elevation of the differential unit shown in Figure 1;

Figure 4 is a sectional elevation along line 4-4 of Figure 3;

Figure 5 is an elevation of a reproducer rotor? toFigure 6 is a side elevation of a reproducer ro- Figure '7 is a sectional elevation of a reproducer stator, a wiring diagram being superimposed upon the elevation; and,

Figure 8 is an elevation of a complete secondary clock embodying the reproducer unit.

In Figure 1, reference numeral i indicates the shaft driven by motor M which is placed in an abutting relationship to and drives transmission shaft Ii through a coupling comprised of two disks [2 and i3 positioned at the end of each shaft, respectively, pins 14 being afilxed to one disk and extending through slots in the other so that shaft ll may move axially with respect to shaft [0. A collar I is mounted on shaft II which has an annular groove formed therein so that a laterally reciprocable member, 24, extending into the groove can engage the collar to displace the shaft one way or the other, the shaft being slidably mounted in suitable bearings not shown. A pinion ll amxed to shaft l l engages a wheel II on countershaft II and wheel I! on shaft H is adapted to engage a pinion 20 on the countershaft when shaft II is displaced to the left, this displacement disengaging pinion and wheel I. and I1. An idler II is mounted on a suitable idler shaft,'not shown. so that it will be engaged by wheel II when the wheel and shaft are displaced to the right. The idler in turn engages a pinion 23 mounted on the countershaft and serves to reverse the rotation of the countershaft.

The pin which engages the collar I5 is mounted on the arm 2! which extends upwardly from armature 26, the armature being associated with a core 21 and pivoted thereon at 28. Windings 2i and I each surround a separate branch of the core so that as one or the other is energized the transmission shaft H is displaced to the left or to the right. As shown in this embodiment, shaft ll normally rotates at a speed of revolutions per hour and'the speed ratio between shaft II and countershaft II, when the armature is in the normal or intermediate position, is six to one. When the armature is displaced in either direction the ratio is one to six so that the speed of rotation of the countershaft is normally twenty revolutions per hour but is increased to 720 revolutions per hour upon energization of either of the windings 28 and 30. the rotation in one instance being in the reversed direction.

A wheel 3| is mounted on rotor shaft 32 near one end thereof and engages pinion 23 on the countershaft so that the shaft is normally roopposite end of the shaft 32 from gear wheel II.

The motor also drives one element of a differential which comprises a shaft 40 having idler wheels 4i and 42 mounted thereon on either side of a fixed wheel 43 which rotates with the shaft. Wheel 38 engages and drives idler 4|. Mounted on idler 42 are two stub shafts 44 and 45 on which are mounted pinions 46 and 41, respectively. Pinions 48 and 4'! are of greater width than wheels 4i and 43 so that pinions 46 and 41 will mesh with each other as well as with wheels 4| and 43, respectively. Wheel 4! drives the idler 42, the former wheel being mounted on a shaft 49 to which shaft is also affixed a pinion 5| which is driven by wheel ii on clock shaft 52; the clock shaft forming a part of a continuously running master clock 53 which is here shown only diagrammatically. In the present embodiment master clock 53 is a so-called carryover clock, that is a spring driven clock which also has a synchronous electric motor 'associated therewith so that the speed of the clock is normally controlled by the synchronous motor but during current interruptions the speed is controlled by a balance wheel in the usual fashion. An example of such a clock wherein a synchronous motor oscillates one end of the hair spring of a clock, and thereby controls the frequency of the oscillations of the balance wheel is described in U. S. Patent No. 2,088,972. In this clock the main spring actually drives the clock at all times. In other types,. the synchronous motor may drive the clock normally, means being provided to connect the spring driven clockwork to the clock during current interruptions. Such a clock of course will run at all times, whether the circuit to the synchronous motor is interrupted or not, and normally the operation of this clock is synchronized with the operation of the synchronous motor M which drives the rotor 33.

A single tooth pinion 54 is amxed to shaft 40 and engages a star wheel 55 which in turn is mounted on shaft 56 so that each rotation of the shaft 40 will rotate the star wheel by an amount equal to one tooth. A click, I ll, is provided to prevent casual rotation of the star wheel during are suitably positioned concentrically to shaft 56 and are insulated from each other by insulating segments 62 and 63. A slip ring 64 is mounted on, and insulated from shaft 56 and a wiper 55 extends from the slip ring and engages one of the conducting or insulating segments. A brush 6B is adapted to contact the slip ring.

.With reference to Figures 1 and 2, which show the electrical circuits for the various elements above described, reference numerals II. and 12 are A. C. lines. A conductor 13 extends between line 12 and wiper 65, and the conducting segments 60 and SI are in series circuit with relays l6 and 11, respectively, through conductors I and 15. Conductors l8 and 19 extend from relays 15 and I1, respectively, to common conductor 86, and thence to A. C. line H. Contacts 80 and iii which are operated by relays 16 and 11 are placed between conductors 82, 84 and 83 and 85, respectively, the contacts being in circuit with windings 30 and 29, the energization of either of which will move the armature 26 in one direction or the other to control the operation of the transmission. Springs 88 and 89 extending from either side of armature 26 are suitably anchored in the frame work of the transmission so that when neither of the windings '30 or 29 are energized, the armature will remain in a neutral position which determines the normal operation of th transmitting unit. A common return conductor 81 extends from windings 30 and 29 to A. C. line H.

Motor M is connected to the A. C. source of supply by conductors 90 and 9| and the synchronous motor 98 of the master clock is connected to said source by conductors 92-and 93. Conductors 94 and 95 lead from lines H and 12, respectively, to brushes 36 and 31, respectively, of the generator, so that winding 99 of the rotor may be energized by the standard sixty cycle A. C. current. The stator I of the generator is provided with coils H which are star connected and conductors I02, I03 and HM lead from the star connected coils of the generator to similarly star connected coils of one or more reproducers R.

In normal operation, the motor M drives rotor 33 and idler II at a constant rate of speed, and the master clock drives idler 42 at a constant rate of speed, the speed ratio between idlers H and 42 being such that whel 43 remains stationary and wiper 65 is at rest in contact with insulating segment 62.

If the master clock is set ahead manually. the action of the difierential will cause wiper 55 to be rotated in the clockwise direction into contact with segment 8|. A circuit will thereupon be established from line 12 through conductor 13, wiper 65, segment 6|, conductor 15, relay l1, conductors l9 and 86 to line H. Energization of relay I1 will establish a circuit from line 12 through conductor 83, relay contacts 8|, conductor 85, magnet winding 29 and conductor 81 to line H. Energization of electromagnet 29 will attract armature 26 and cause axial displacement of transmission shaft H, disengaging pinion IG from wheel I! and engaging wheel l9 with pinion 20. This increases the speed ratio between the motor and the rotor shaft, thereby increasing the .rotor speed and causing the reproducer rotors to catch up with the master clock. At the same time idler 4| is rotated at greater than normal speed; consequently the action of the differential will cause wiper 65 to be rotated in the counterclockwise direction back to its-normal position thereby opening the above mentioned circuits and causing operation of the transmission at its normal speed ratio. At this time, the secondaries are again in synchronism with the master clock.

If the master clock is set back, wiper 65 will be rotated in the counterclockwise direction establishing a circuit from line 12 through .conductor 13, wiper 65, segment 60, conductor 14, relay l6, conductors I8 and 88 to line ll. Energization of relay 16 will establish a circuit from line 12 through conductor 82, relay contacts 90, conductor 84, magnet winding 30, and conductor 81 to line 1 I. Energization of magnet 30 will attract armature 26 which will displace transmission shaft II to the right, disengaging pinion 16 from wheel l1 and engaging wheel 19 with idler pinion 2|. tween the motor and the rotor shaft, but in the reverse direction, causing the hands of the secondary clocks to move backward until they are in agreement with the master clock, at which time wiper 65, by virtue of the increased speed of idler II in the reverse direction, will have rotated in the clockwise direction along segment 60 to its normal position in contact with insulating segment 62.

A current interruption has the same eflect as setting the master clock ahead, for during the interruption the wiper is rotated in the clockwise direction, and upon resumption of the current supply the circuit conditions are similar to those described after the master clock has been set ahead.

Normally, the single tooth pinion 54 engages the star' wheel 55 so that a slight angular displacement of wheel 43 and the single tooth pinion will be suflicient to throw the wiper of! insulating segment 62 into contact with one of the conducting segments.

Inasmuch as the position of the wiper on either one of the conducting segments is immaterial, it is possible to employ intermittent motion transmission means between diflerential shaft 40 and wiper shaft 58 whereby a slight angular displacement of shaft 40 will cause the corrective mechanism to operate as above described, but further rotation of the shaft ll will rotate shaft 58 'at a much lower average speed ratio. If idler ll is locked due to a current interruption, the master clock will drive shaft lll through the differential, at a speed of five revolutions per hour, or sixty revolutions per 12 hours. Star wheel 55 is provided with sixty teeth, consequently it will rotate once every twelve hours during a current interruption. No matter at what time the current This increases the speed ratio be-' supply is resumed, or no matter how great the error between the master clock and the secondaries, the wiper will be in contact with one or the other of the conducting segments and eflect correction of the secondaries. It will be further noted that if the error is greater than six hours, for instance, if the current interruption has lasted for ten hours, that the hands will move to indicate the correct time by the shortest route; in this instance the wiper will be incontact with segment 60 which will cause the hands to move backward to the extent of two hours rather than forward ten hours. Consequently, by the employment of the above described intermittent motion transmission means, we dispense with the coarse and fine controls of the prior art wherein the coarse control corrected for the number of whole revolutions of error and the fine control corrected for the fractional revolution of error or discrepancy between the generator rotor and the reproducer rotors. It is of course, obvious that this feature of our invention is useful in other applications of self-synchronizing systems than the corrective clock system herein shown.

As shown in Figure 2, motor M is a self-starting synchronous motor and the master clock is provided with a self-starting synchronous clock motor 98'. In this embodiment it is assumed that lines II and I2 are provided with A. C. of a regulated frequency. Consequently the two motors are synchronized with respect to each other, and as the motor 98 controls the speed of the master clock, there would be no need for correction during normal operation. If the A. C. is not of regulated frequency, however, the master clock may be of any type which keeps accurate time, and motor M may be any type of motor. In this instance, as the motor M and the secondary clocks fall behind or advance with respect to the master clock, correction will occur more frequently. The more nearly the motor M approaches a constant speed motor, provided it is geared down so that the rotor is rotated at the proper speed ratio with respect to the master clock shaft 52, the less frequently will correction occur. It will therefore be noted that this system may be used whether the A. C. supply is regulated or not. The A. C. for energization of' the current supply for rotor 33 will render the.

reproducers inoperative, it is essential that the rotation of the rotor cease within half a, revolution after said current interruption, and to accomplish this, the motor and the rotor may be energized by the same source of current supply, or if this is not practicable, a relay in the rotor supply circuit may be provided to control the motor supply circuit accordingly.

The generator is essentially the same in construction as the reproducer which is shown in detail in Figures 5, 6 and 7 with the exception that the rotor of the former is wound and is provided with the necessary slip rings and brushes, all of which may be dispensed with in the reproducer. The generator, furthermore, is somewhat larger in size than the several reproducers.

The reproducer rotor H in Figure 6 is comprised of a plurality of laminations Il2 rigidly associated with the shaft H3 in the customary manner by means of collars I I4. Although the laminations are .of the same shape and size,each

one is angularly displaced from its adjacent laminations so that the rotor as a whole is skewed.

The stator III in Figures 7 and 8 is also composed of a plurality of larninations, III, which are held together by studs IIO. Frame plate III and I3I in which rotor shaft 3 is journaled, are associated with the stator laminations by the studs H0 as shown in Figure -8. The stator is slotted as at I I0 to form twelve poles H3, and six coils I 20 to I25 are positioned in the slots, the construction of the stator and the coil connections being the same as those of a star connected alternator.

As indicated in Figure 7, in which the wiring diagram is superimposed upon a section of the stator taken between two adjacent laminations, the coils are paired, each member of a pair being in series with the other, coils I20 and I2I, coils I22 and I23, and coils I24 and I25 being connected by conductors I20, I21 and I20, re-- spectively. The free end of coils I2I, I23 and I25 are connected to lines I02, I03 and I04, respectively, and the free end of coils I20, I22 and I24 are connected together by neutral wire I20.

If the rotor were provided with a straight edge, or one parallel to a slot IIO, the rotor would not come to rest at a position wherein its edge would be opposite a slot as this would increase the air gap, and this tendency to avoid such a position is a cause of an error in the positioning of the reproducer rotor, the error herein being referred to as the periodic error" because of its periodic occurrence as the rotor is caused to rotate through 360 degrees. Skewing the rotor has the effect of eliminating in large part the periodic error for there is no unstable position of the rotor with respect to the slot. Furthermore, with respect to the generator, the skewed rotor serves to distribute the flux of the primary more evenly throughout the stator with the result that the strength of the primary field cutting each coil progressively increases from a minimum at those points in the stator which are intersected by the axis of the primary coil to a maximum at those points degrees therefrom. Therefore, if each coil has an equal number of turns, the voltage and current induced in each coil increases as the axis of each secondary coil approaches parallelism with the axis of the primary coil, the increase being gradual as the receding skewed edge intersects each slot and causes more of the primary flux to be diverted around the coil in that particular slot rather than being shunted across the air gap of the slot.

The complete secondary clock is shown in Figure 8 and comprises front and rear plates I30 and I3I, respectively, which are spaced from each other by pillars I32. Reproducer R is suitably mounted on the rear plate which also comprises one of the frame plates of the reproducer. Rotor shaft H3 is suitably journaled in the reproducer frame plates H1 and I 3|, terminating in a pinion I33. Minute shaft I34 is suitably journaled in the front and rear plates and carries wheel I35 engaged by pinion I33 and by means of which the minute shaft is driven by the rotor shaft in a l to 5 ratio. A dial I 30 is associated with the front plate and hands I31 and I30 cooperate with the dial in the usual manner, minute hand I31 being aflixed to shaft I34 and hour hand I30 being affixed to sleeve I39 which is associated with the minute shaft by appropriate reduction gearing I40.

Any periodic error that is not corrected by the skewed rotor construction will be negligible in extent as it appears on the clock face due to the reduction gearing between the rotor shaft and the minute shaft,

Various other modifications and changes in the circuits and Wiring, and in the apparatus above described, as well as changes in the sizes and proportions of the parts thereof, which will occur to those skilled in the art, may be eifected without departing from the spirit of our invention, as defined by the following claims, and all statements regarding the operation of our invention are intended to be illustrative only and not limitations on the said claims.

We claim:

i. In a self-synchronizing system, a generator and reproducers in circuit therewith, means for driving said generator, control means, a diiierential one element of which is associated with said generator and another element of which is associated with said control means, means actuated by said differential for regulating the speed at which said generator is driven, said latter means including the group comprising a brush and a commutator, intermittent motion transmission means for associating said differential with one element of said group, said commutator comprising two conducting segments separated by an insulating segment, a circuit including said brush and one of said conducting segments and means for increasing the'speed at which said generator is driven in the forward direction, a circuit including said brush and the other of said conducting segments and means for reversing the direction of rotation of said generator, an initial rotation of slight extent of said differential in 'either direction from a neutral position causing relative rotation of said brush at a predetermined rate of speed from a neutral position in contact with said insulating segment to -a position in contact with one or the other of said conducting segments, and further rotation of said difierential causing relative rotation of said brush at a lower average rate of speed.

2. A self-synchronizing system comprising a first member, the rotation of which is to be reproduced by a second member, a self-synchronizing generator and a reproducer in circuit with said reproducer, driving means for said generator, 8. difierential driven by said driving means and by said first member, control means associated with said differential for regulating the speed at which said generator and said differential are driven by said driving means, said generator normally being rotated at a higher rate of speed than said first member, and speed reducing means posaid control member, means associated with said differential for regulating the rotation of said rotor in either direction, a self-synchronizing reproducer in circuit with said master generator, a driven rotatable member associated with said reproducer, speed increasing means between said control member and said differential and corresponding speed reduction means between said reproducer and said driven rotatable member whereby said speed increasing and decreasing means reduce any error between said rotatable control member and said driven rotatable member which is caused by the periodic error between said master generator and said reproducer.

4. A self-synchronizing system comprising a. generator, a plurality of reprodu'cers in circuit therewith, driving means for said generator, means for increasing the absolute speed of said generator in either the forward or reverse directions, two electromagnets, an armature common to both and adapted to be moved by the energization of either of said electromagnets, said armature being associated with said speed increasing means to actuate the same,'independent circuits for said electromagnets, a rotatable control member, dliierential means responsive to the rotation of both said control member and said generator for registering correspondence of position or positive or negative difference between the actual position of said generator and the position thereof corresponding to the actual position of said control member, and automatic switching means actuated by said difierential means when a positive or negative difference is registered for selectively completing one or the other of said independent circuits.

5. A self-synchronizing system comprising a master device, a rotatable member, means responsive to diflerences in the corresponding speeds of said master device and said rotatable member for regulating the speed of said rotatelements being associated with said master generator, a master device associatedxwith said other driven element, and a two segment commutator associated with said driving element, speed changing means positioned between said synchronous motor and said master generator, a brush for cooperation with said commutator, electrical means for controlling the action of said speed changing means, an electric circuit including said commutator, brush and electrical control means, and a plurality of self-synchronizing reproducers in circuit with said master generator. FRANK L. EIDMANN.

GEORGE C. ENGEL. 1 ADOLPH AMEND, JR. 

